Gas tube reflective surface ionizable by high energy electromagnetic waves



April 5, 1966 Filed Feb. 27, 1963 T. E. MANWARREN 3,245,008

GAS TUBE REFLECTIVE SURFACE IONIZABLE BY HIGH ENERGY ELECTROMAGNETIC WAVES 2 Sheets-Sheet 1 WAVE- GUIDE OUTPUT TR/-2O --TR TUBE WAVEGUIDE WAVEGUIDE INPUT OUTPUT F|G.3 DZ' E TR UNIT v A 2 2 H 1 2 TRANSMITTER HYBRID ANTENNA LOAD HYBRID RECEIVER TR UNIT INVENTORZ THOMAS E. MANWARREN,

HIS ATTORNEY.

Aprll 5, 1966 T. E. MANWARREN 3,245,008

GAS TUBE REFLECTIVE SURFACE IONIZABLE BY HIGH ENERGY ELECTROMAGNETIC WAVES Filed Feb. 27, 1963 2 Sheets-Sheet 2 TR TUBES FOCAL POINT 62 INVENTOR THOMAS E. MANWARREN,

BY fiwfl W HIS ATTORNEY.

United States Patent 3,245,098 GAS TUBE REFLECTIVE SURFAGE llONIZABLE BY HIGH ENERGY ELECTROMAGNETIC WAVES Thomas E. Manwarren, Fernwood, N.Y., assignor to General Electric Company, a corporation of New York Filed Feb. 27, 1963, Ser. No. 261,444 14 Ciaims. ((31. 33313) This invention relates to the transmission and reception of microwaves and in particular it relates to microwave switches or duplexers permitting the alternate transmission of high power signals and the reception of weak signals through a single antenna system.

Known prior art devices include combinations of special TR tubes (or transmit-receive tubes) with resonant cavities in which the TR tubes are placed at or near the center of the cavities. These prior art devices have the desirable eflect of reducing the RF, or radio frequency, current in the glow discharge by a factor related to the input coupling susceptance to the cavity, but present disadvantages which are explained below. A variation of these known prior art devices involves the use of a reactance in series with the glow discharge of a TR tube. This latter configuration serves to reduce the RF current in the discharge by a factor related to the value of the reactance used. Both known configurations of these prior art devices are placed in a resonant cavity and consequently they both have the disadvantage of reducing the instantaneous bandwidth of the signal which can be transmitted to a value proportional to f Q where is the central frequency and Q is the loaded Q of the cavity. In addition to reducing the bandwidth, both of these systems increase the insertion loss for low level signals. Another limitation of the prior art devices is that they are functional only as lumped or distributed parameters which means they must be of small size relative to the wavelengths of the energy being handled and may not be employed to form images with, or to collimate, the energy received It is therefore an object of this invention to provide a transmit-receive device capable of handling high power RF signals without a reduction in bandwidth.

It is an additional object of this invention to provide an improved transmit-receive system which is not-limited in bandwidth by resonant devices,

It is a further object of this invention to provide a duplexer capable of operating with only a single TR tube, or else with a number of TR tubes placed together to function as a unit,

It is another object of this invention to provide a duplexer having the ability to control large amounts of energy and at the same time to transmit a wide bandwidth limited only by the capacity of the waveguides used to feed the device,

It is still another object of this invention to provide improved bandwidth and power handling capabilities in a radar transmit-receive element with small insertion losses,

It is yet another object of this invention to reduce the current density of the RF current in the glow discharge of a transmit-receive device,

It is still a further object of this invention to provide means for transmitting low level and for reflecting high level electromagnetic energy such that a controlled plane or curved constant phase contour is formed in the reflected high energy wave,

It is yet a further object of this invention to provide means for transmitting low level and for reflecting high level electromagnetic energy so that, depending on the curvature of the reflecting-transmitting means, real or virtual images may be formed from the reflected and/or the transmitted energy, and

It is yet another object of this invention to provide improved means for collimating high power electromagnetic signals.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a sectional view of an embodiment of this invention,

FIG. 2 is a view of another embodiment of the invention showing some details in perspective,

FIG. 3 is a block diagram of a duplexer which incorporates elements like those shown in FIG. 1 and in FIG. 2,

FIG. 4 is a sectional plan view of an embodiment of the invention of use as a complete duplexer,

FIG. 5 is a sectional view or" an embodiment of the invention also of use as a complete duplexer, and

FIG. 5a is perspective view of a TR device suitable for use in the duplexer of FIG. 5,

FIG. 6 is a sectional view of yet another embodiment of the invention of use as a complete duplexer.

FIG. 6a is a perspective view of an alternative form of TR device suitable for use in the duplexer of FIG. 6.

Briefly, the invention involves the receipt of RF signals into a volume of ionizable gas having a relatively large dimension perpendicular to the direction of propagation of the RF signals and shallow depth in the direction of propagation of the RF signals. In a preferred embodiment of the invention, this configuration of the gas volume is provided by expanding the area of a vessel containing the gas in a way to enlarge its cross sectional area to impinging RF signals. If the RF signals are of low energy level they will pass through the gas with little or no eflect, but if the RF signals are of high energy level they will ionize the gas and subsequent high energy signals will be reflected by the ionized gas. Reflections from the ionized gas will be able to form virtual images when the ionized gas is held in containers so that it presents either a flat configuration or one having a convex curve on the signal receiving side. The reflections will be able to form real images if they come from a concave curve on the side on which the high energy RF signals are received. The reflections will be directed back along the path traveled by the RF signals if the ionized gas is held in fiat or tubular vessels.

Turning to FIG. 1, we find an embodiment of the present invention located between a waveguide input at 2 and a waveguide output at 4. Waveguide sections are shown as sectional views of FIG. 1 at 6 and 8 with sections expanded in either the E plane or the H plane, or both, as indicated at It and 12. The expanded waveguide sections are connected through a transmit-receive tube, or TR tube, which is labeled TR-Z. In the configuration shown in FIG. 1, high energy microwaves supplied to the waveguide input at 2 and through waveguides at 6 and 10 will impinge on the TR tube TR-2 and gas contained in the tube will be highly ionized so that most of the energy will be reflected back through the waveguide sections 10 and 6 to the waveguide input at 2 for transmission through a suitably coupled antenna. In receive periods, low energy signals received by the antenna can be accepted through the waveguide input at 2, through the waveguide sections 6 and 10 and through the TR tube TR-2. These low energy signals will produce no ionization in the tube due to their low energy level so that received signals can pass through the TR tube and the at TR-2 are shown -in the copend-ing application of Thomas E. Manwarren and'Robert J. Jones, Serial Number 225,939, filed on September 24, 1962, now Patent No. 3,209,285 and assigned to the U.S. Government. These tubes consist of concentric glass walls which are closely spaced throughout their greater length, -somewhat as the tubes used in? embodiments of the presentinvention as indicatedby the bracket-11 in- FIG. 1, but have a relatively large opening, such as, is indicated by 'bracket '13, between them at one end. The small space -between the glass walls in the'longer :-portion of the tube -serves as a shallow space in which an easily ionized gas such as argon maybe confined --for ready ionization. The larger open space at one-end ot:-the tube serves as -a reservoir for additional gas molecules as the "gasis gradually dissip'ated into the glass w'alls'of the tube. In the configuration of the-invention shown in FIG. 1, the total energy incident on the T RF-Z --tube wouldbe about the same *as would'impinge on the tube if the tube were placed in e the input waveguide fl. However, by the use of the configuration shown in-FIG. -1 with 'an-expanded area-along the sides of the tube TR-2, the current density at any :point i-n'the glowdischarge isreduced. The amount of the reduction in the current density is a factor'roughly :proportional'to the area-of the tube exposed to the input signal.

The invention as shown in FIG. 1 within the dashed :line 9 may be called a -T R unit for'conve-n-ience *and has been-so'labeled. The use of this .term TR unit will be "helpful in'describing the application -of the invention as s'hown'in FIG. 1 to a'conrplete'duplexer circuit, such as that illustrated in FIG. 3. In FIG. 3 the transmitter T 2 supplies a high power microwave signaltoia conventional hybrid device or hybrid waveguide junction, -H-'-2, such as isconventionally used 'in microwave circuits. -In such hybrids a received signal from asource'such as T may be split 'to be transmitted to TR units such as those indicated at D-2 and D-4. With high'energy microwaves being transmitted from the hybrid to the TR units D2 and D 4, a state of ionization will be provided in the TR tubes contained in the TR units. This ionization will provide virtually total reflection of the microwave signals back to the hybrid and from there to the antenna for transmission. Reflected microwave signals from-suitable targets which are received at the antenna -A-2, on the other hand, will be relatively weak and will be transmitted through-the hybrid H-Z to the 'duplexe'rs D-2 and D-4 where they will produce no ionization of the gas in the TR tubes and will be transmitted to the hybrid H 4 and the receiver R*-2. The load indicated by the block L-Z, it will be recognized, is primarily a means of disposing of any high energy microwave sig'nalswhich may leak through the TR units -D-2 and D-4.

A device such as the TR unit of FIG. 1 will function satisfactorily in con-junction with a complete circuit such as that shown in FIG. 3, providing the aperture of the waveguide and of the tube "PR- 2 is not too large relative to the waveguide members '6 and 8. It the aperture is made too large, that is if the large dimension along the tube TR2 is too great, phase errors may be generated which will distort the uniform phase front which is desired for energy reflected by the TR tube or transmittedby it. If phase errors'are generated, there will be reflection losses forlo-w level energy passing trom one side of the tube to the other. One way to remedy this situation is to shape the TR-Z tube sothat when the ionized gas es function as a mirror reflecting high energy signals, the mirror is shaped to reflect each part of the Wa'veback alon'gthe path through which it came. The shapeof the tube can at the same time be made so that it functions like a lens to transmit low energy signals without aberration.

Another embodiment of the invention, which avoids these problems and allows further reductions in current density, is shown in FIG. 2. In the devices shown in FIG.

2, energy from a feedhorn at 20 is reflected from a surface having a parabolic curve or a parabola'at 22 to form arplaneconstant' phase contour inoidenton the TR tube TR-20.. Low level energy from waveguide input -20 passesthroughthe'tube TR- 20, is reflected by a second .parabola at"24, -and focused on the teedhorn 26 with very little loss. High level energy'o'n-the other hand ionizes :the gas in tube TR-Qi) which then actsas a reflector to a-reflect the energy back to ;parabola.22. The .iparabola 22 then reflects the'ener'gy to the feedhorn-20 which translimits the energy through'the waveguide input-tor further use. This complete device acts 'as a bandpass transmit- "receive device and two of them can be used' ina balanced duplexer when connected as shown in FIG. 3 in place The embodiment of -the invention 'shown in FIG. -2

is expected that, E or H i-plane rpillboxes should 'suflice to handle transmitted power levels higher than can now be generatedpconsequently expansion oftbe zparabolas to three dimensions n presently'unnecessary. It isof interest to note that-the 'Eiplane TEM pillbox offers a distinct advantage over the H plane type in that all RF current in the tube flows parallel 'to the tube axis and there is no RF current flowing into the flow discharge from the pillbox metal walls except at the ends. At'the 'ends, the'current density in the tube can be made small 'by'designing the feedhorn 'to illuminate the :parabola er iparabolic contour at a low power level. A folded or double 'layer pillbox of conventional design may be used ing generated at the horns by energy reflected back-to the born from the central portion of the parabola. In each a folded pil-lb-ox, a feedhorn such as 20 in FIG. 2 would be 'in a separate chamber of the pillbox'p'a'ra'llel to the-chambers'hown in FIG. 2. High level energ trom'rhe -feedhorn would be transmitted't-hrough a passage connecting the two chambers along the curve 22 to ionize the gas in tube TR20 and be reflected back.

An 'addit-iona'l embodiment of the invention is shown in a sectio'na'l view in-FIG. 4 where a circular pillbo'x at 40 has four horns spaced apart and arranged 'to 'face the inner wall of the circular pillbox. The four horns have been labeled T-40, tor transmitter Ehorn, A40 for antenna horn, L-40 for load horn and R 40 for receiver horn. These horns are shown-with suitable 'po'rts a't *P-40, P-4 1, P-42 'and P- 43 respectively through which microwave'sig'nals may be transmitted. In this cdirfigurationonly one TR tube, -shownas TR40, is required to completed the. duplexi'ng 'tu-hctioh. The TR tube in this instance may be of cylindrical cross section, 'ratherfth'an being flat sided or of other curved shape, since most of the reflections in a flat walled pillbox of this kind will be properly oriented if reflected by idn's held in a cylindrical tube. In the operation of the embodiment of the invention shown in 'FIG. 4,'high level energy received through the port P 40 of the transmitter input horn indicated at T40 is reflected off the inner side of the circul-ar'w'all'of the pillbox 40. The circular-contour of the pillbox 40 functions satisfactorily as a collimating device providing a .proper choice is made of the F/D ratio where Fis the focal length of-the horn and D is the length of a chord along the are illuminated on the inside of the circular pillbox. In this connection, it will be recognized that with the proper ratio of F to D the circular contour approximates a parabola. The highly collimated signal reflected off the inner face of the circular pillbox is a plane wave which will :be incident on the TR tube TR-"40 at an angle of 45 with respect to the tube axis. This high power s-ignal ionizes the gas within the tube, as previously explained, and is reflected in the form of a plane wave to impinge upon the circular wall facing the antenna horn -A-40. The signal is reflected by a section of the cylindrical wall of the pillbox and focused at the antenna output arm horn A-40 for transmission through the port P-41 to the antenna, which is not shown. Any high power microwaves which leak past the tube TR-40 will be focused by the interior of the circular pil-lbox into the load output horn L-40 and will be dissipated by a load circuit connected to the output port P-42 in the manner described with respect to FIG. 3.

During receive periods, the duplexer shown in FIG. 4 will receive low level energy from the antenna arm through a port P-41 and through the horn A-40. This low level energy will be reflected *from the interior wall of the pillbox opposite the horn A40 and transmitted as a collimated signal through the un-ionized tube TR-40 to be reflected by the opposite Wall of the pillbox and focused at the receiver arm R-40 for transmission through the port P-43 to the receiver. The curved walls of the pillbox may be cylindrical walls, or parabolic walls, or may be folded into a double layer with the feedhorn in a separate layer in order to avoid reflections caused by the presence of the feedhorn blocking the apertures. It will be recognized that the embodiment of the invention illustrated in FIG. 4 need not be confined to a shallow pillbox, but that it may be expanded in two planes as much as desired in order to increase the power handling ability of the system. The tube TR-40 may be cylindrical in shape with its greatest dimension along its axis, as indicated.

An additional configuration of the invention in which the duplexer actually becomes a part or" the antenna feed is illustrated in FIG. 5. In the operation of the apparatus shown in FIG. 5 high intensity energy radiated from a transmitter horn at T-50 will ionize the gase in TR tubes at TR-50 and be reflected from the plane reflector formed by the TR tubes to the face of a parabola or paraboloid at 50 to form a virtual image of the transmitter horn at the parabola or paraboloid focal point. The receive horn R-SO is isolated from the transmitter horn during transmit periods because of the TR tubes which may be a number of tubes placed side by side, as FIG. 5a illustrates by way of example, or a large flat tube or tubes. During a receive period energy collected by the paraboloid will pass through the un-ionized TR tubes and be focused at the focal point of the paraboloid which is also the receiving point of the receive horn R-St).

The TR tubes of FIG. 5 may be shaped in a particular manner by bending or by flattening and then bending to vary the eifective focal length during the transmit period as in a Cassegrainian telescope system such as is illustrated in FIG. 6. FIG. 6 shows a transmitter horn at T-60 located approximately at the vertex of a paraboloid antenna 60 with a small aperture in the center of the paraboloid through which high powered signals may be passed. The transmitted signals strike one part of a hyperb'oloid shaped configuration at 62 which is composedeither of a single large TR tube (see FIG. 6a) or a number of small TR tubes designated at TR-62 such that gas in the tubes becomes ionized and reflects the high energy signals into the face of the paraboloid at 60. The paraboloid 60 then transmits the signals in the desired collimated fashion. During the receive time, the paraboloid 60 will reflect received signals through the hyperboloid 62 to the receive horn R-60 for use as previously described.

The relative dimensions of the TR tubes employed in embodiments of this invention are of such significance to the invention that further comments are in order. It has been noted that most, if not all, of the prior art TR tubes have been limited in size to cross sectional areas which are small enough so that their operating parts could be contained within the Walls of waveguides. The cross sectional dimensions of waveguides are generally smaller than a wavelength, consequently the prior art TR tubes have also been constrained to be smaller in their maximum usable dimensions than a wavelength. With such small dimensions, the prior art TR tubes have functioned only as lumped or distributed parameters which concentrated energy in a small volume and have been incapable of forming images. With the much larger dimensions of embodiments of the present invention, new relationships are brought into play and the TR tubes may be categorized as collimating and/or focusing devices. Such collirnating and focusing devices can distribute energy over a much larger area than can lumped parameters so that high energy levels are less likely to be damaging. In addition to providing more efiective means for controlling the transmission of large amounts of energy, the introduction of relatively large TR elements makes it possible to focus both high and low level energy to form either real or virtual images, depending on the curvature of the TR elements.

While the principles of the invention have now been made clear, there will be immediately obvious to those skilled in the art many modifications in structure, arrangement, proportions, the elements and components used in the practice of the invention, and otherwise, which are particularly adapted for specific environments and operating requirements without departing from those principles. The appended claims are therefore intended to cover and embrace any such modifications within the limits of the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A reflector for high energy microwave comprising a closed container having walls spaced in close proximity relative to the length of the container, an ionizable gas contained in the space between said walls, said closed container having a shape corresponding to that of a desired reflector, said closed container and said ionizable gas being transparent to low energy microwaves, and said closed container operating as a reflector capable of forming real images from said high energy microwaves when said ionizable gas becomes dissociated into its ions under bombardment by said high energy microwaves.

2. A reflector for high level electromagnetic energy comprising a closed container having Walls spaced together in close proximity relative to the wavelength of said high level electromagnetic energy, an ionizable gas contained in the space between said walls, said walls having a shape corresponding to that of a desired reflector, said closed container having a dimension in at least one direction of a magnitude at least equal to the Wavelength of said high level electromagnetic energy, said closed container and said ionizable gas being transparent to low level electromagnetic energy and said ionizable gas functioning as a reflector capable of forming an image from said high level electromagnetic energy when said ionizable gas becomes dissociated into its ions under bombardment by said high level electromagnetic energy.

3. A reflector for high level electromagnetic energy comprising a closed container having walls spaced together in close proximity relative to the wavelength of said high level electromagnetic energy, an ionizable gas contained in the space between said walls, said walls having a shape corresponding to that of a desired reflector, said closed container having a dimension in at least one direction of a magnitude suflicient to enable the formation of an image from said high level electromagnetic energy, said closed container and said ionizable gas being transparent to low level electromagnetic energy and said ionizable gas functioning as a reflector having said desired shape when said ionizable gas becomes dissociated into its ions under bombardment by said high level electromagnetic energy.

4. In a duplexer for transmitting low energy microwaves and for'refiecting high energy microwaves, means iilluding a closed container having a configuration such that it ma be placed to filla pathway of said'microwaves, said closed container iiidofpoiating a tliin volume of ionizable gas within contoured walls, said closed container and ionizable gasbcing transparent to low energy microwaves but said ionizable gas'becoming dissociated into its ions in thepresence ofhigh energy microwaves to form a reflector shaped by said contoured walls, said reflector serving to form images of said high energy microwaves along-lines perpendicular to the, direction of propagationof said high energy microwaves.

5. In a duplexer for transmitting low energy microwaves and for'reflecting high energy microwaves, means including a passageway for transmitting said microwaves, a closed container having a configuration to effectively fill saidpassage'way, said closed container incorporating a thin volumeof ionizable gas within contoured walls, said closed container and ionizabl'e gas remaining transparent to low energy microwaves, but said ionizable gas becom ing dissociated into its ions in the presence of high energy microwaves to form areflector shaped by said contoured walls, said reflector serving to-form images of said high energy microwaves in planes perpendicular to the direction o'f-;propagati on of said high energywaves.

6, I a microwavecontrol devie for transmitting low energyjmicr'owaves and forreflecting high energy microwaves, means including a passageway for transmitting said microwaves, means including an expanded section of said passageway expanded in at least one plane to a size substantially equal to the magnitude of a wavelength of said high energy microwaves, means for effectively filling-said expanded section oflpassageway including a closed container, said closed container incorporating a thin volume of ionizable gas, said closed container and ionizable gasremaining transparent to low energy microwaves, bu t saidionizahlegas' becoming dissociated into its ionsiin the presence of high energy microwaves to form a reflector for said high energy waves said reflector serving-to form-imagesof said high energymicrowaves along lines perpendicular. to the direction of propagation of said highenergy waves.

7, A wavc controlli ng device comprising plural layers of material sealed to forrn'closed spaces, an io'nizable gas fillingsaid spaces, saidlayers, of materialthaving radii of curvature of selected magnitude to form surfaces of a shape such that suitable coatings would cause them to reflect energy to form images, saidsurfaces and enclosedgas beingtransparent to,low energy microwaves, said enclosed'gas becoming ionized in the presence of high energy. microwavesto forn a reflecting Zone. shaped by said surfaces; saidreilecting zone being of shapesuch that the images-iorrned by reflection therefrom are along lines perpendicular to the direction of propagation of the reflected wave, i

8. A deviceforseparating low energy. electromagnetic waves frorn high energy electromagnetic waves and for focusing said separated high energy electromagnetic waves comprising acontainer having closely spaced Walls of selected curvature, said container enclosing a quantity ofionizable gas, said walls; and ionizable gas being transparent to low energy electromagnetic waves, said ionizable gas becoming dissociated into its ions when subjected to high energyelectromagnetic waves and acting as arefl'ector, saidselected curvature of said closely spaced walls determining the shape of saidreflector and the plate at which saidhigh energy-waves may be focused. I

9. A device for separating low energy electromagnetic waves from high energy electromagnetic waves. andv for focusing said separated high energy. electromagnetic waves comprising a container having closely spaced walls. of selected curvature, said container enclosing a quantity ofionizable gas, said walls and ionizable gas being .trans parent to low energy electromagnetic waves, saidionizable gas becoming dissociated into its ions when subjectedto high ehergy electromagnetic waves and acting. as a re-. flector, said selected curvature of. said closely spaced walls determining the sha e of. said reflectorianddhe place at which said high energy waves maybe focused, said close. ly spaced walls having larger extent than a wavelength in a direction perpendicular to the directionof propagation of said electromagnetic waves to form said reflector and to reduce the concentration of electromagnetic energy.

ltr. A device for separating low energyelectromagnetic waves from high energy electromagnetic waves audio: focusing saidseparated'high energy electromagnetic waves comprising a container. havingcloselyspaced walls-of selected curvature, saidcontainer, enclosing a, quantity. of ionizable gas, said walls andionizahle gasibeing trans,

parent to lowenergy electromagneticwaves, said ionizable,

gas becoming dissociateddnto, its ions when subjected 'to high energy electromagnetic waves and-acting as a, re; flector, saidselected. curvature of saichclosely, spaced walls cletermining t'he shape'of said reflector and thelplaue. in which said high energy waves may be focused, andlthe extension of saidclosely spaced walls tov dimensions greater than a wavelength of sa-idv electromagnetic waves in a direction perpendicular to the direction of propaga-, tion of said electromagnetic waves. serving toi ,red uc,e the concentration of electromagnetic energy .per unit volume of said reflector. i

11. A controller for electromagnetic waves comprising means including a closed container for confining aquantity of ionizable' gas, said closed containerhaving walls of desired shape selected to restrain said ionizable gas within a volume of space havingfa particular shape, said ionizable gas transmitting low energy electromagnetic signals, said ionizaole gas respondingtohigh energy electromagnetic signals to become ionized, and said gas, on being ionized form ing. a reflecting. zonev within said Walls of desiredshape to reflect saidhigh energy electromagnetic signals" to form focu-sed'images at least along one line in aplane perpendicular to the directionofpropagw tion of said electrom agneticvwaves.

12. A reflector substantially as claimediinclairn 1 in which said closed container comprisesa plurality ot'long tubular sections having independent closures. of gas.

13. A reflector substantially as claimed infclairntl in which said closed container comprises apluralityof long tubular sections having independent closures of gas.

14. A reflector substantially as claimed'in claim 3.in which said closed container comprises a plurality of long tubular sections having independent closures of gas.

References Cited by, the Examiner UNITED STATES 2,085,406 6/1937. Zwqrykin 343 1 2,543,130 2/1951 Robertson 343 18 2,688,744 971954 Siinstcin 343+7Q1 X 3,126,546 3/1964 Noji' 343%7'01 3,147,450 9/1964. Sleeper n 333 -13 HERMAN KARL SAALBACH, Primary Examiner. Cr, TABAK, E. LIEBERMAN, Assistant Examiners, 

6. IN A MICROWAVE CONTROL DEVICE FOR TRANSMITTING LOW ENERGY MICROWAVES AND FOR REFLECTING HIGH ENERGY MICROWAVES, MEANS INCLUDING A PASSAGEWAY FOR TRANSMITTING SAID MICROWAVES, MEANS INCLUDING AN EXPANDED SECTION OF SAID PASSAGEWAY EXPANDED IN AT LEAST ONE PLANE TO A SIZE SUBSTANTIALLY EQUAL TO THE MAGNITUDE OF A WAVELENGTH OF SAID HIGH ENERGY MICROWAVES, MEANS FOR EFFECTIVELY FILLING AND EXPANDED SECTION OF PASSAGEWAY INCLUDING A CLOSED CONTAINER, SAID CLOSED CONTAINER INCORPORATING A THIN VOLUME OF IONIZABLE GAS, SAID CLOSED CONTAINER AND 